Why do we want to reset the loop

Don't think of it in terms of resetting the loop, think of it in terms of resetting the call to the database that returns the values. For instance, say I want to list 5 similar articles on the side bar of a news website. But the side bar code is above the main article code. So I tell Wordpress, "hey find me 5 articles that have the same tag as this one." So Wordpress gets that from the database and I run it through a loop to print it out. Now I want to print the main article but Wordpress doesn't have that information stored in the $posts array. So now I need to tell WP to get that info, and since the main article is the default value return from the database for that page I would just "reset the loop".